1. Technical Field
The present invention relates to a semiconductor integrated circuit, and more particularly, to a signal generating apparatus that is capable of measuring a trip point of a power-up signal and a method of measuring a trip point of a power-up signal using the same.
2. Related Art
In general, a power-up signal as a type of switching signal is a signal that supplies an elevated voltage to a semiconductor integrated circuit.
This power-up signal is generated at the time of applying a voltage to a system to which a semiconductor integrated circuit is applied. That is, the power-up signal is generated by a voltage (hereinafter, referred to as external voltage VDD) that is supplied from the outside. The power-up signal is generated in the signal generating apparatus to which the external voltage VDD is supplied. When the input external voltage has a voltage level that is equal to or higher than a predetermined voltage level, the voltage level of the power-up signal is shifted from a high level to a low level. In this case, the timing when the voltage level of the power-up signal is shifted from the low level to the high level is referred to as a trip point of the power-up signal.
Generally, when the power-up signal is at a low level, the semiconductor integrated circuit performs a reset operation to prepare a normal operation. If the voltage level of the power-up signal is shifted from the low level to the high level, the semiconductor integrated circuit performs a normal operation.
In order to perform a stable operation in a system to which the semiconductor integrated circuit is applied, it is necessary to measure a power-up trip point. That is, the power-up trip point needs to be generated before the semiconductor integrated circuit operates. However, the power-up trip point may be generated during the operation of the semiconductor integrated circuit due to a process variable and a low voltage used. Thus, it is necessary to measure the power-up trip point and perform a trimming operation such that the power-up trip point is generated before the semiconductor integrated circuit operates.
However, when the power-up trip point is measured, each power-up signal generating unit needs to monitor a voltage change corresponding to a time change by using a measuring instrument, such as an oscilloscope. For this reason, a test is complicated and it is difficult to accurately measure the power-up trip point.